Investments in Securities Available-for-sale Securities 1 (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	$ 5		$ 15		$ 32		$ 148
Gross realized losses	3		22		13		75
Total proceeds	$ 44	[1]	$ 597	[1]	$ 444	[1]	$ 1,826	[1]

[1] Excludes proceeds from the initial sale of securities from new portfolio securitizations included in “Note 2, Consolidations and Transfers of Financial Assets.”